605

Asian-Aust. J. Anim. Sci. Vol. 20, No. 4 : 605 - 614

April 2007

www.ajas.info

Environmental Sustainability and Social Desirability Issues in Pig Feeding*

T. S. Yang** Division of Applied Biology, Animal Technology Institute Taiwan, P.O. Box 23, Chunan, Miaoli, Taiwan, ROC

ABSTRACT : Feeding pigs used to be a means of managing domestic resources that may otherwise have been wasted into valuable animal protein. Feeding pigs thus was a form of husbandry. Following recent rapid industrial development, pig rearing has changed from extensive to intensive, but this transformation has been associated with major concerns. The concentration of large amounts of pig manure in small arrears is environmentally hazardous. Moreover, high densities of animals in intensive production systems also impose a health threat for both animals and humans. Furthermore, the use of growth promoters and preventive medicines for higher production efficiencies, such as in-feed antibiotics, also induces microbial resistance thus affects human therapeutics. In addition, consumers are questioning the ethics of treating animals in intensive production systems. Animal welfare, environmental and bio-safe issues are re- shaping the nature of pig production systems. Feeding pigs thus involves not only the consideration of economic traits, but also welfare traits and environmental traits. Thus, a focus on technological feasibility, environmental sustainability and social desirability is essential for successful feeding operations. Feeding pigs now involves multiple projects with different sustainability goals, but goal conflicts exist since no pattern or scenario can fulfill all sustainability goals and the disagreements are complicated by reduced or even no use of in- feed antibiotics. Thus it is difficult to feed pigs in a manner that meets all goals of high quality, safe product, eco- and bio-sustainability, animal welfare and profit. A sustainable pig production system thus requires a prioritization of goals based on understanding among consumers, society and producers and needs to view from both a local and global perspective. (Key Words : Pig Feeding, Environmental Sustainability, Social Desirability)

INTRODUCTION animal-derived food consumption. The increase in real incomes of consumers and in urbanization has led pork to The judicious use of domestic resources to cultivate or be produced in intensive systems, thus lowering the cost of produce of plants and animals is known as husbandry. The production through economies of scale. Industrial pig use of pigs as converters, rather than scavengers, to production is capitally and technologically intensive, and is transform farm left-over or kitchen swill to favorable also highly labor efficient. It drives trade in feed grains and animal products not only provides organic fertilizer for other feed resources, and thus is detached from land in crops, but is also beneficial for nutrient management, and terms of feed supply and waste disposal. Consequently, pig undoubtedly constitutes husbandry. Pigs under such a production is fairly transportable, since it is not restricted to minimum waste system of conventional agriculture are highly specific geographic locations (grain producing areas) traditionally kept in small herds as a sideline source of farm or climate conditions (temperate environments). The revenue. Following industrial developments and economic application of controlled environment measures has enabled growth, pig rearing has rapidly industrialized and changed pig production in a range of disfavoring regions (tropical from extensive to intensive due to greater demands for and subtropical) around the world. Therefore, pig husbandry has evolved into commercial pork production * This paper was presented at the 4th International Symposium on through the adoption of modern technologies of animal th Recent Advances in Animal Nutrition during the 12 Animal science, and knowledge of finance and commerce, to meet Sciences Congress, Asian-Australasian Association of Animal the consumption needs of urban consumers with high Production Societies held in Busan, Korea (September 18-22th, disposable incomes. 2006). ** Corresponding Author: T. S. Yang. Conversely, industrial systems of pig production cause E-mail: [email protected], Division of Applied Biology, some substantial concerns. The concentration of large Animal Technology Institute Taiwan, P.O. Box 23, Chunan, quantities of pig manure in small areas is hazardous to the Miaoli, Taiwan, ROC. environment. This problem is aggravated by the expansion 606 T. S. Yang (2007) Asian-Aust. J. Anim. Sci. 20(4):605-614 of metropolitan areas, and the placing of production near recycling. LCA is a tool to assess the environmental large cities to allow good market access. High densities of impacts of product systems and services, accounting for the animals in intensive production systems also impose a emissions and resource usage during the production, constant health threat for both animals and humans. The use distribution, use and disposal of a product (ISO 14045, of growth promoters and preventive medicines for higher 1999). It also includes methods for grouping different efficiencies, such as in-feed antibiotics, also induces emission based on the extent of the environment impact microbial resistance, and consequently affects human caused when released. The effects of eutrophication and therapeutics through horizontal gene transfer or survival global warming, which are mainly based on input-output niche movement. Some swine exotic diseases also analysis by LCA approaches, are utilized as indicators to significantly increase the risk of zoonoses. Moreover, inform policy making, select areas of action, identify the consumers, who have been benefited by the low cost and most sustainable methods, advise consumers and evaluate secure supply of industrial production, are questioning the the effectiveness of sustainable consumption or production ethics of raising animals in intensive systems, and are measures, when considering sustainable consumption and increasingly willing to pay more for similar products with production. This assessment can help producers to reduce ethical as well as ecological values. Environmental issues, the environmental impact of a product during its life cycle, animal welfare and safety are particularly important in the such as in pig production, addressing the energy in feed knowledge-based economy, and have moved animal formulation and consumption when rearing a pig herd, as production beyond the singular goal of providing animal well as the environmental load linked with the disposal or products and maximizing profit. treatment of pig manure. Environmental, bio-safe and animal welfare issues are The environmental impact of pig production in a life changing pig production systems, requiring effective cycle perspective has previously been described (Basset- management of resources such as water, soil, air and Mens and van der Werf, 2005). High nitrogen utilization is biomaterials from microbials to feed materials, along with generally agreed to be the most important measure for respect for animal rights. Therefore, feeding pigs is not only reducing hazards of acidification and eutrophication in a pig a consideration of economic traits such as growth rate, lean production system. The European Union’s Nitrate Directive percent, feed efficiency and litter size, but also (91/676/EC), which permits a maximum of 170 kg N/ha to environmental traits (e.g. less excretion of N and P) and be applied to cultivated land each year to keep the N welfare traits (e.g. little stereotypies, maternity, fitness and concentration of surface water below 50 mg nitrate/L, disease resistance). Producers seeking a fair income for indicating that a manure surplus in particular N surplus is their current work and investment are facing challenges, considered as an threat to water quality. because feeding pigs should not only be environmental Reducing N loss from the farm must begin with proper friendly and biologically safe, but also be accommodate animal feeding and management to reduce N excretion. A social ethics. Hence, the technological feasibility, low-protein pig diet has been recommended to improve the environmental sustainability and the social desirability are environmental performance, and can be achieved by essential for successful operations. including a large quantity of synthetic amino acids (Han and Lee, 2000; Han et al., 2001). Indeed, lowering the ENVIRONMENTAL SUSTAINABILITY dietary crude protein level from 16% to 12%, and supplementing the diet with crystalline lysine, tryptophan Life cycle assessment and threonine, could significantly decrease the level of N New incentives and policies for ensuring the excretion, provided that growth performance and lean tissue sustainability of agriculture and ecosystem services are gain are similar in growing pigs whether they are housed in crucial to ensure that food meets the growing demand a thermal-neutral or heat-stressed environment (Kerr et al., without compromising environmental integrity and public 2003). health (Tilman et al., 2002). Feeding pigs involves multiple Several general strategies of nutrition and feed environmental projects, and involves two major management besides amino acid supplementation exist to sustainability issues: eutrophication or acidification, and reduce nutrient excretions and odors from pig manure. global warming or energy consumption. The environmental Avoiding excessive overages of dietary P, balancing diets impact of pig production can be described as a life cycle. A on the basis of available P, and use of phytase, are practical comprehensive set of programs focusing on sustainable pig for reducing the level of P in manure (Knowlton et al., production should employ the life cycle assessment (LCA) 2004). Use of reduced or organic forms of Cu, Zn, Fe and to promote production patterns. The fundamental principle Mg decrease excretion of these minerals in manure. of the LCA is to follow the product through its entire life Maintaining the proper acid-base balance and buffering in cycle from extraction of raw materials to final disposal or the diet can significantly lower odorous compounds. T. S. Yang (2007) Asian-Aust. J. Anim. Sci. 20(4):605-614 607

Additionally, adding acidifying Ca salts to the diet rather fermentable carbohydrates are showing considerable than CaCO3 could lower urinary pH, and consequently promise as dietary agents capable of increasing bacterial decrease ammonia emission by 26 to 53% (q.v. Sutton and populations considered advantageous to host health or, Richert, 2004). alternatively, in suppressing those that may promote Effluent from pig farms also contains large quantities of pathogenesis (Crittenden et al., 2002). Therefore, selecting electrolytes, creating additional difficulties. A high appropriate carbohydrate sources is beneficial for both N electrical conductivity ranges from 2,000 to 6,000 µs/cm, emission and animal health, as well as for public health, depending on the amount of flush water used in cleaning, because it reduces the use of in-feed antibiotics to manage was recorded from a family-based small production unit. colonic problems. This level far exceeds the maximum limit of 750 µs/cm, 25°C for crop irrigation. Two periods of irrigation with Priority of impact attributes maximum conductivity allowance generally build up a soil The impacts on the environment attributes of pig limit of 4,000 µs/cm at which can retard crop growth (Yu et production also include energy consumption and related al., 2005). Channeling the pig farm effluent into irrigation environmental parameters (Su et al., 2003). Feed production system is therefore detrimental to crop field, and rice paddy has a large impact on the overall environment system, and may be the most vulnerable crop due to continuous wetting. contributes more than animal rearing per se to the Attempts to minimize electrolyte content in pig excreta to environmental burden. Thus, raw materials selection during reduce conductivity by dietary modification have not been diet formulation determines the environmental impact, successful. Decreasing dietary protein content by 20%, and because each material used differs in energy required to mineral supplements by 40% (Ca, P and other salts), would produce. A Swedish study (Strid Eriksson et al., 2005) reduce nutrients supply close to maintain level of pigs. revealed that the impact parameters of pigs fed on a diet However, this level could only decrease waste water based on imported soybean meal were 6.8 MJ, 1.5 CO2-eq, conductivity by 30%, leaving it well beyond the irrigation 0.55 O2-eq, and 24 SO2-eq per kg gained. However, allowance (Yu et al., 2005). The conductivity is significant, changing the diet to a formulation based on Swedish especially in areas where pig feeding and crop growing produced peas and rapeseed cake led to lower parameter often co-exist in integrated farming systems within a small values of 5.3 MJ, 1.3 CO2-eq, 0.55 O2-eq and 25 SO2-eq per close community. An independent watercourse is kg gained. Their study indicates that high levels of peas undoubtedly a burden if it becomes a prerequisite for rather than soybean meal should be suggested to Swedish feeding pigs. pig producers to reduce energy use and global warming Dietary carbohydrate manipulations have recently potential. By contrast, the same set of input data creates an attracted significant interest, because it can not only reduce opposite conclusion of minimal acidification and environmental impact by lowering ammonia emission from eutrophication are focused and locally produced peas manure, but also act as a prebiotic, allowing it partially to should be avoided from pig diet in Sweden due mainly to replace in-feed antibiotics. Including fermentable the increasing use of fertilizers to produce crops locally carbohydrates in diets has reduced the ratio between urinary (Strid Eriksson, 2004). This dilemma also applies to N and fecal N, reducing emission because fecal N is less inclusion of synthetic amino acids into pig diet, possibly easily degraded to ammonia. Additionally, slurry pH is also reducing eutrophication but also increasing energy use as reduced, which further decreases the potential for urease well as cost. Thus, an environmental impact priority e.g. activity and ammonia volatilization (q.v. Nahm, 2003). A eutrophication and acidification verses global warming and linear relationship was found between the intake of dietary energy use should be made before an appropriate nonstarch polysaccharides and ammonia emission. For each production system could be operated. 100g increase in the intake of the nonstarch polysaccharides, Quality and safe pork product are currently also the slurry pH fell by about 0.12, and ammonia emission emphasized and indoor pig production with specialized decreased by 5.4%. Practically, the use of raw potato starch integration is essential for the production system. Certified rather than cornstarch in the diets of growing pigs lowered production (e.g. HACCP) can only be achieved using well- ammonia emission by 13% (Lenis and Jongbloed, 1999). controlled operations, where the hosing environment as Resistant potato starch also led to a dose-dependent well as diet formulation and distribution are controlled to reduction of skatole in the gut content from 134 µ/g dry maximize nutritional and hygienic values. Animal health is matter (controls) to 4.8 µ/g in the treated group. Back fat also monitored, and preventive medical treatment is used. skatole concentrations were decreased from 159 to 20 ng/g The subsequent slaughtering and packing should be clearly fat and belly fat concentrations from 64 to 16 ng/g fat also effectively regulated to certify product quality and (Losel and Claus, 2005) and significantly improved odor safety. Such a product-quality scenario inevitably has a control from pig facilities (Willig et al., 2005). Furthermore, higher environmental impact than the eco-friendly system 608 T. S. Yang (2007) Asian-Aust. J. Anim. Sci. 20(4):605-614 of efficient use of feed resources (Stern et al., 2005). By known bacterial gene transfer mechanisms (Seveno et al., contrast, if animal welfare is the major concern, then 2002). Multiple classes of antimicrobial compounds were animals should have outdoor opportunities, be able to detected in swine slurry lagoons, nearby surface soil, access to a paddock, and be raised in groups to avoid re- ground water samples, and pig farm dust (Compagnolo, ranking and fighting. Strategic feeding is applied with diets 2002). The exposure pathway for transfer of resistant diluted with forages to increase the feeding time. Mental organisms from pigs to humans thus has become multiple. enrichments by providing stimuli (e.g. bedding, toys) are Inhalation of air at an intensive production site (Hamscher also encouraging, and maternal traits are also important for et al., 2003; Chapin et al., 2005), and drinking nearby selection and breeding. The management practice should be ground water have also become pathways (Krapac et al., chosen to achieve high hygienic feed quality and a healthy 2002). Removing antibiotics from pig rations is imperative physical environment for the herd. This animal welfare to minimizing public health concerns associated with scenario shows an in-between environment impact among intensive pig farming. systems of quality ensuring and efficient use of resources, A recent increase in the incidence of severe E. coli- but has the highest production cost because of larger space associated diarrhea in piglets has been observed worldwide. needed required to produce animals (Stern et al., 2005). Severe forms of E. coli are likely due to the emergence of Environment, product health and animal welfare each virulent E. coli clones and intensified production systems focus on one aspect of sustainability, and sometimes (Fairbrother et al., 2005). Bacterial resistance to antibiotics conflict with each other. Therefore, the environment and a recent increase in the prevalence and severity of post sustainability of pig feeding should vary in its meaning, weaning syndromes have created a hostile environment for structure and approaches, based on location, economic and pig production. Decreasing subtherapeutic antibiotic use is social conditions. Eutrophication and acidification are obligatory; however, producers have a difficult time finding important factors in a large production unit, so controlling consistently effective substitutes with acceptable costs. For the emission of N and other substances is the top priority. decades, producers have relied on in-feed antibiotics to Thus, phase feeding and efficiently used slurry should be maintain health and growth of herds raised in sub-optimum adopted. A family production unit in rural areas may sanitary environments and, consequently, many producers orientate to the quality-safety pattern, although it has the believe such antibiotics are a necessity. A sudden highest value for energy use, global warming potential, withdrawal of in-feed antibiotics typically causes an chemical use and surplus nutrients. A welfare system immediate production loss particularly in subtropical and appears to be essential for units close to metropolitan areas. tropical environments. A great loss in efficiency is primarily It should be noted that feeds selection, diet formulation, and due to gastro-intestinal problems in early weaned pigs even feeding strategies differ between systems, and thus affecting when supported by health management plans. Alternative pork quality (Olsson and Pickova, 2005). That is different strategies of feeding to the use of in-feed subtherapeutic production systems may have different market niches, antibiotics are being developed and extensively reviewed by resulting in different breeding goals such as for socially Adjiri-Awere and van Lunen (2005). Generally, these important traits (Kanis et al., 2005). No feeding pattern or strategies can be classified as growth promotion or disease management system has yet been found to fulfill all prevention-the latter is more urgently needed. sustainability goals of pig production, and the Numerous studies have shown that beneficial effects disagreements could be further complicated by public can be attained through diet modification, including health requirements, such as compulsory reduction or non- supplementation with prebiotics, probiotics, synbiotics, use of in-feed antibiotics. minerals, organic acids, nutraceuticals and herbs. Feeding pigs with probiotics, or living microorganisms such as lactic SOCIAL DESIRABILITY acid producers (lactobacilli and bifidobacteria), streptococci, yeast and saccharomyces species, has shown that these Reducing antibiotic-resistance threats microorganisms may be substituted for in-feed antibiotics in Although markedly enhancing growth performance, high-health nurseries (Kritas and Morrison, 2005). However, antibiotic use in intensive pig production has contributed to in-feed antibiotics have minimal impact on healthy animals the development and persistence of multidrug-resistant under clean conditions (Taylor, 1999). Substituting bacteria (Cromwell, 2002; Verstegen and Williams, 2002). probiotics for antibiotics requires a practical value, Subtherapeutic doses of in-feed antibiotics have been especially in sub-optimum sanity or “dirty” conditions in shown to select bacteria for resistance to high which in-feed antibiotics are needed and their advantageous concentrations of antibiotics (Aarestrup et al., 2000a, effects can be exerted the best. 2000b). Furthermore, antibiotic resistant genes have Additionally, not all probiotic strains are effective and become highly mobile and their spread has occurred by all there exists considerable strain-to-strain variations in T. S. Yang (2007) Asian-Aust. J. Anim. Sci. 20(4):605-614 609 characteristics relevant to probiotic efficacy within bacterial specific nutrient sources beneficial to microorganisms and, species. A special strain may be more effective or more when ingested in small quantities, can effectively stimulate specific-for example, the B. lactis strain of HN019 is preferential growth, although not exclusively of lactobacilli effective in decreasing severity of rotavirus-induced and bifidobacteria (Tzortzis et al., 2005). Other prebiotics diarrhea in weaning piglets. By feeding HN019, Shu et al. frequently mentioned are gentio-oligasaccharides, isomalto- (2001) demonstrated that the content of fecal rotavirus and oligosaccharides, xilo-oligosaccharides, soybean oligo- E. coli could not only be lowed, but blood leukocyte saccharides, in addition to lactulose, lactosucrose and inulin. phagocytic and T-lymphocyte proliferate responses, as well In early weaned pigs, supplementation with FOS and as gastro-intestinal tract pathogen-specific antibody titers lactobacillus significantly improved weight gain and feed were elevated in weaning pigs. Therefore, the protective efficiency (Estrada et al., 2001). When infected with effect of HN019 is likely via a mechanism accounting for Salmonella typhimurium, 2-day-old piglets did not develop enhanced immune-mediated protection and inter-microbial diarrhea when fed a diet containing 7.5 g/L FOS (Correa- competition with pathogens for intestinal attachment sites. Matos et al., 2003). The effectiveness of these prebiotics in Probiotic strains may be wholly or partially reliant on more monogastric animals depends on initial concentration of than one mechanism for protection against gastro-intestinal indigenous prebiotic species and intra-luminal pH (Duggan pathogens. et al., 2002). Prebiotic oligosaccharides are currently Interest in probiotics has been fuelled in recent years by utilized as functional food ingredients for human use and an increasing number of animal and human studies thus, their use in animal feed is cost-prohibitive. demonstrating the beneficial effects of probiotic cultures on Non-digestible carbohydrates, including resistant numerous health conditions, including reduced atopic starches (RS) and fiber-like non-starch polysaccharides eczema symptoms and severity and duration of gastro- (NSP), which have also shown promise as prebiotics intestinal infections, particularly rotavirus infections (Doron (Brown et al., 1997), beneficially modify intestinal function and Gorbach, 2006). Probiotics may not be consistently of weaning piglets and other mono-gastric animals. Not all successful; however, when bacterial cell numbers are starch is digested and absorbed in humans and pigs. inadequate, contaminated or aged, bacterial cultures lose Resistant starches, named for their resistance to amylolysis, their efficacy and instability of intestinal fermentation. Pig occur in many foods, e.g., whole grains and seeds, raw producers often find that studies are not applicable under potatoes and green bananas. Relatively high starch actual intensive production units as many factors affect concentrations have been detected in terminal ileum and probiotic survival in feed preparations. Well-known factors large bowel of pigs fed diets containing different starches such as pH, temperature, and oxygen, variations in starter (Brown et al., 1997; Bird et al., 2000). Studies of pigs fed cultures (Shihata and Shah, 2002), prebiotics, oxygen various starches have demonstrated that RS is a significant scavengers (Dave and Shah, 1998), water activity and sugar substrate for large bowel microflora, and that excretions of concentrations (Shah and Ravula, 2000) all dramatically bifidobacteria ingested orally were higher than in those influence probiotic survival during storage and feeding. consuming normal starches (Brown et al., 1997). Consequently, effectiveness can vary among farms, places Interest in RS as a prebiotic developed from the and times and seasons. A dynamic program of probiotic appreciation that consumption of large amounts of RS led to feeding is required for practical use and should be based on a time-dependent shift in fecal and large-bowel profiles of studies with well-defined strains and/or products, animals short-chain fatty acids (SCFA), primarily acetate, from well-defined backgrounds in randomized, well- propionate and butyrate as end-products of colonic controlled trial designs with appropriate numbers to fermentation. Butyrate is the major energy source for calculate significance. These conditions are essential for colonocytes, whereas propionate is largely taken up by the conducting clinical trials that have results of practical value. liver and acetate enters peripheral circulation and Inclusion of nondigestible or fermentable carbohydrates metabolized by peripheral tissues. Specific SCFA may in pig diet is a practical approach for controlling ammonia reduce risk of developing gastrointestinal disorders and it is and reducing nitrogen excretion as mentioned earlier. likely that some or all of the effects of RS are through the However, equally important, fermentable carbohydrates actions of SCFA (Wong et al., 2006). Interest is increasing reportedly have significantly affected monogastric animals regarding prebiotic potential; for example, in children with by encouraging proliferation of select groups of colonic acute diarrhea, adding amylase-resistant starch to glucose miroflora (Brown et al., 1997). A number of non-digestible oral rehydration shortened diarrhea duration compared with oligosaccharides, which have been shown to selectively that achieved with a standard treatment (Raghupathy et al., promote proliferation of bifidbacteria in the colon, and are 2006). In weaning piglets feeding a diet based on cooked recognized as prebiotics. For example, fructo- rice (high in RS) supplemented with either animal or plant oligosaccharides (FOS) and galacto-oligosaccharides are protein lowers the incidence and severity of diarrhea with a 610 T. S. Yang (2007) Asian-Aust. J. Anim. Sci. 20(4):605-614 consequent reduction in mortality (Montagne et al., 2004). are at high risk of developing diarrhea (Kim et al., 2005). This finding is of particular interest for pig producers in Far Directly adding organic or inorganic acid to weaning diet or Eastern regions where low-cost locally grown rice is readily drinking water is an alternative approach to providing a available. Suitably processed rice may be a useful feed favorable acid environment and it has been shown to option for pig herds in which post weaning colibacillosis is improve feed efficiency and enhance growth performance endemic and resistant strains of E. coli are present. in piglets (Franco et al., 2005). Both FOS and RS raised fecal bifidobacteria numbers The practice of diet acidification by adding organic by roughly equal amounts when fed separately to pigs. In a acids in excess of 2.7 kg per ton is becoming more popular human study, these increases are of a generally similar order as a method of reducing feed pH and controlling enteric to those reported for prebiotics such as FOS (Tuohy et al., pathogens in growing pigs. At such high acid levels, 2001). When fed FOS and RS together, an increase palatability becomes a problem for weaning piglets-they exceeding individual increases suggests that they operate reluctant to eat dry feed and avoid acidified diets when through different mechanisms. Furthermore, FOS and RS given a choice. Adding 1.2% of K-diformate to acidify maintain colonies in pigs when probiotics supplementation piglet diet does not decrease feed intake or negatively affect ceases. Thus, when pigs were fed a control diet, fecal piglet dietary preferences (Ettle et al., 2005). Notably, bifidobacteria numbers declined rapidly following probiotic minimizing the addition of alkaline compounds such as withdrawal. However, this decline was much slower than calcium bicarbonate or protein from fish and milk products that in those fed either FOS or RS. When FOS and RS were helps to optimizes the benefits of diet acidification resulting consumed together, no decline existed in fecal numbers from decreasing buffering effects (Kornegay et al., 1994; (Brown et al., 1997). Maximal effectiveness may be Hardy, 1999). achieved when preparations could be a mixture of FOS and Other compounds, including botanicals, nutracenticals RS, as these agents seem to have additive effects. Also, and anti-microbial peptides, have been proposed as combining several probiotic bacteria will achieve stronger alternatives to in-feed antibiotics, and, although not yet effects and this effect was the same as combing different applicable, have generated promising results. Some herbs prebiotic (oligosaccharides and RS). Thus, to formulate are valued for their medicinal properties, flavor or aroma. It synbiotics (probiotic with prebiotics) can be likened to an has been suggested that many plant extracts and spices act art as different environments require different strategies. as immuno-modulators when administered in low doses and Availability or the source of RS, selection of probiotic show great promise as feed additives to replace current strains, palatability considerations, manufacturing antimicrobial agents. Garlic, ginseng, and oregano are (pelleting), storage, etc., all render formulating a new frequently used as general tonics in alternative human generation of carbohydrate-manipulated diets complex. medicine and, thus, are of limited use for animals due to Fermentable carbohydrate in certain circumstances is availability and cost (q.v. Adjiri-Awere and van Lunen, detrimental rather than beneficial to pigs. For example, the 2005). Investigations of the medical values of herbs, incidence of pig dysentery can be largely reduced with a although often using pigs as experiment animals, usually low NSP diet (Pluske et al., 1996, 1998). This reduction is have minimal practical use for pig production. Identifying simply because colonization by spirochaetes is highly the active compounds and ingredients in plant extracts with related to dietary NSP concentrations, while incidence of the most potent antimicrobial action and growth-promoting dysentery was also reduced when diet included low RS efficacy is essential before these compounds can be (Durmic et al., 2002). Further studies are now required, commercially produced and applied in animal production. given the diverse nature of carbohydrate substrates and the Development of novel anti-infection agents to cope with SCFA patterns produced by their fermentation. Studies are the antibiotic-resistance threat is urgently needed in human also required to quantify the health benefits of prebiotics and animal medicine. A source of compounds considered and synbiotics and their interactions in different feeding promising is the large number of gene-encoded environments. antimicrobial peptides in animals and plants. These peptides Luminal acidification as reflected by low fecal pH is a are also termed bacteriocins and are constitutively produced positive response to diet containing probiotics, prebiotics or or synthesized following infection or injury. Mammals have synbiotics feeding. Additionally, maintaining intestinal a large variety of antimicrobial peptides that function as luminal pH at approximately 4.5 is necessary to support natural innate barriers suppressing microbial infection, or, proliferation of beneficial bacteria and exclude gut in some instances, they act as integral components in pathogenic. This low luminal ph is particularly important response to inflammation or microbial infection (Brogden et for weaning piglets as they suffer environmental and al., 2003). These peptides have board-spectrum activity psychological stressors during transit and develop a high against a wide range of microorganisms, including Gram- gastric pH when milk diet is replaced by dry feed and, thus, positive and Gram-negative bacteria, protozoa, yeast, fungi T. S. Yang (2007) Asian-Aust. J. Anim. Sci. 20(4):605-614 611 and viruses (Reddy et al., 2004). The so-called epithelial acid attachments have been suggested as alternatives to defensins that are produced by Toll receptors once the inorganic compounds. Supplemental lower concentrations bacteria are recognized are actually comparable with (500 ppm) of Zn from ZnO or several organic sources, antibiotics (Ganz, 2003). however, did not stimulate growth, feed intake, or In pigs, more than a dozen distinct anti-microbial efficiency (Hollis et al., 2005). Feeding pharmacological Cu peptides have been identified, some of which include is also advantageous to weaning and growing pigs (Davis et defensins. These peptides are naturally present in the al., 2002), as is high dietary Mg to finishing and market gastro-intestinal tract and act as a common mechanism of pigs (Apple et al., 2005). Yet, again these supplementations host defense (Zhang et al., 2000). High (20-200 µg/ml) generate waste treatment problems. concentrations of porcine β-defensin are expressed in the Supplementary tryptophan is a nutritional therapy aimed dorsal tongue (Zhang et al., 1999), and are synergistic with at modifying pig behavior (Li et al., 2006). In nursery pigs other porcine antimicrobial peptides against E. coli and during weaning and mixing, diets containing high multidrug-resistant salmonella. Some bacteriocins are in tryptophan (5 g/kg feed) decreased neuroendocrine commercial production; for example, nisin is used to components of stress and increased gastro-intestinal control bacterial spoilage in heat-processed, low-pH food robustness but behavioral reactivity was not affected worldwide; lactoferrin along with some probiotics is (Koopmans et al., 2006). When seeking new methods for employed as health food supplement. However, use of improving health and welfare of early weaned piglets, re- purified or recombinant bacteriocins in animal rations is evaluation of the current weaning program is worthwhile. unlikely in the foreseeable future simply because these are All the efforts to improve the well-being of early weaned not cost-effective. Immuno-modulation to enhance in vivo piglets may not be equivalent to allowing them an extra expression, synthesis and release of bateriocins is likely a week of nursing, which may be more beneficial to piglets. feasible approach. Sows and pregnant gilts often exhibit repeated oral/nasal behavior when limit fed and housed in penned Animal welfare crates. The stereotypies that indicate poor animal welfare Intensive animal production systems are also criticized can be decreased by feeding high-fiber diets (Meunier- for poor animal treatment. These debates focus on how farm Salaun et al., 2001). This diet has an additional advantage animals live and housing and feeding conditions. These of increasing the number of piglets born (Grieshop et al., concerns are reflected in current legislation and regulations 2001). On the other hand, Holt et al. (2006) demonstrated (e.g., space allowance) that will have a considerable impact that feeding a high-fiber diet with 40% soybean hulls to on pig production and will modify the feature of pig rearing gestating sows did not enhance sow welfare by reducing facilities and management tools, thereby increasing pig stereotypical behavior or reduce cortisol concentrations. production costs. To resolve confinement-related animal Such a high-fiber diet also reduced digestibility and welfare problems, providing an environment that suits decreased reproductive performance with fewer pigs born, animal needs is the predominant approach. Therapeutic as compared with that of sows fed a control diet. Moreover, practice is also involved, including the use of chemicals, feeding gestating sows twice daily instead of once did not nutritional therapy and other treatments to effectively improve their behavior or reproductive performance. The suppress undesirable behavior associated with product varying response of sows to high dietary fiber diets suggests quality assurance programs. For instance, synthetic that many factors influence the efficacy of dietary fiber; the maternal pheromones are utilized to reduce fighting and fiber composition of various ingredients is certainly worthy stimulate feeding behavior, thereby improving the well- of further investigation. being of early-weaned piglets (McGlone and Anderson, By definition, dietary fiber comprises a broad spectrum 2002). Supplementing diet with antibiotics was also a of components. Cellulose and hemicelluloses comprise the therapeutic approach as it enhances pig health and welfare; principal substrates fermented in the large intestine. Studies however, this practice has been criticized due to concerns using diets with different fermentable carbohydrates would about antibiotic resistance. clarify the efficacy of dietary fiber to improve welfare and Feeding pharmacological concentrations of ZnO (2,000- reproductive performance since, after fermentation, dietary 4,000 ppm) to weanling pigs reduced the incidence of fiber generates readily absorbed short chain fatty acids and diarrhea (Poulsen, 1989) and was considered an approach to beneficially influences animal physiology as mentioned. improving animal welfare. However, such a high Zn Feeding high-fiber diets to sows or gilts may generate a supplementation generated environmental concerns larger amount of manure and create additional environment associated with high Zn concentrations in manure (Mantovi hazards. This environmental effect would not be present if et al., 2003). 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